Mashable

In the 1880s, Hans Jakob Schmid, an employee of Swiss printing company Orell Gessner Füssli, developed a process to produce colorized images from black and white photographic negatives.

Dubbed “Photochrom,” the process was complex and closely guarded. It entailed coating a tablet of lithographic limestone with a light-sensitive concoction, placing it under a reversed halftone photo negative and exposing it to sunlight for up to several hours. The coating would harden in proportion to the level of exposure, and the less hardened portions would be removed with a solvent, forming a fixed lithographic image on the stone.

To produce color, additional litho stones were prepared for each tint in the image. A single color print could require as many as 15 individual tint stones. Though the process was painstaking and delicate, it produced color images which could be remarkably lifelike at a time when true color photography was still in development.

The process was licensed to the Photochrom Company of London and the Detroit Publishing Company, the latter of which had exclusive rights to print Photochroms in the United States.

The Detroit Publishing Company used the process to turn tens of thousands of photographs into color postcards, which were becoming tremendously popular with the 1898 passage of the Private Mailing Card Act, which allowed privately produced postcards to be mailed for half the price of a letter.

Before the postcard craze ended with World War I, the Detroit Publishing Company printed an estimated 7 million photochroms.

Rock formations in Heligoland, Germany.

Image: Library of Congress

The beach at Scheveningen in The Hague.

Image: Library of Congress

The Grand Canal of Venice by moonlight.

Image: Library of Congress

Algerians outside a cafe in Algiers.

Image: Library of Congress

The results combine the truthfulness of a photograph with the color and richness of an oil painting or the delicate tinting of the most exquisite watercolor. The colors are absolutely permanent and attain the virility and strength of nature so often lacking in hand colored work.